Pressure sensitive hot melt adhesive

ABSTRACT

This invention is directed to compositions useful as ionomeric hot melt pressure sensitive adhesive compositions. These compositions comprise a polymer containing carboxylic acid, a miscible metal salt, and an o-methoxy-substituted aryl acid. These compositions display low melt viscosity, simplifyingapplication, as well as improved adhesive properties, especially shear resistance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to compositions useful as improved pressuresensitive hot melt adhesives and for other applications. As novel hotmelt adhesives these compositions display low melt viscosity,simplifying application, as well as improved adhesive properties,especially shear resistance. These compositions are comprised of apolymer containing copolymerized organic acid, a miscible metal salt,and an o-methoxy-aryl acid.

2. Brief Description of the Prior Art

Hot melt pressure sensitive adhesives are tacky, soft materials at roomtemperature. In order to apply these materials to substrates such aspaper, plastic, or cloth, these adhesives are heated to about 250°-350°F. in order to lower their viscosity so that the substrate may be easilycoated. The adhesive coated substrates may then be used as, or used inthe manufacture of, a variety of useful articles such as tapes, labels,decals, et al. A significant limitation on uses for which hot meltpressure sensitive adhesives may be employed is the relatively low shearresistance of these materials. Although these materials have beentraditionally described as solids at room temperature, this descriptionis in a sense erroneous. These adhesives are based on primarilythermoplastic polymers. Thus, although they can exhibit very highviscosity at room temperature, giving the appearance of soft materials,they will flow under an applied stress. Thus they are more accuratelydescribed as high viscosity polymeric liquids at room temperature. Thisnature is reflected in the effect of changing temperature on theviscosity of these materials. As temperature increases there is agradual reduction of viscosity and the materials ultimately attain aviscosity low enough to make coating operations practical. Afterapplication, a temperature decline is reflected in the correspondingincrease in the viscosity of the material. An ideal hot melt pressuresensitive adhesive would exhibit the mechanical properties of a truesolid at room temperature while simultaneously retaining the ability toflow easily at the elevated application temperature. Althoughthermosetting materials as a class have proven impractical for thisapplication, ideally, the pressure sensitive hot melt adhesive wouldbehave as a crosslinked thermoset resin at room temperature: theapplication of shear stress would result merely in deformation and notin flow of the adhesive. Thus the viscosity of the ideal material wouldchange from essentially infinite at room temperature to very low at theapplication temperature. Thus, in a certain sense the magnitude of thisviscosity difference is a measure of quality of the hot melt adhesive.

One approach that has been used in the past to maximize this viscositydifference has been the incorporation of small amounts of functionalmonomers in the adhesive polymer coupled with the use of additionalcomponents to help form thermally reversible crosslinks between thepolymer chains. For example, U.S. Pat. No. 3,925,282, granted Dec. 9,1975, to Davis et al., disclosed acrylic pressure sensitive hot meltadhesive compositions which contain a tertiary amine-containing monomerin the acrylic copolymer. In addition to the copolymer, thesecompositions contain an organo metallic salt which is capable of formingreversible coordinate crosslinks. At room temperature the presence ofthese crosslinks causes the hot melt adhesives to exhibit improvedcohesive strength properties and increased shear resistancecorresponding to higher viscosity relative to the uncrosslinkedmaterial. However, at high temperature the crosslinks are broken and thematerial flows easily. Another type of reversible crosslinking known tothe art of pressure sensitive adhesives is effected when thesecompositions include a divalent metal ion such as zinc or zirconium andcarboxylic acid residues attached to the polymer chain, as disclosed,for example, in U.S. Pat. No. 4,145,467, granted Mar. 20, 1979, to F. T.Sanderson et al.

Another approach has been to include photo initiators in the hot meltcomposition which can be photopolymerized in situ after application ofthe adhesive to the substrate. This approach is exemplified by U.S. Pat.No. 4,052,527, granted Oct. 4, 1977, to S. D. Pastor et al., in whichphotoinitiators are interpolymerized with acrylic copolymers to produceethylenically unsaturated prepolymers. These are applied in hot meltform to the substrate and are subsequently cured by exposure toultraviolet radiation. This approach suffers from the drawbacks ofrequiring: (1) expensive photoinitiators, (2) ultraviolet sensitivityprior to cure, and (3) an additional cure step requiring additionalprocess equipment.

A review of the state of the hot melt adhesive art is presented by thematerials collected by D. L. Bateman in Hot Melt Adhesives (Noyes DataCorp., Third Edition, 1978).

SUMMARY OF THE INVENTION

One of the objects of this invention is a hot melt pressure sensitiveadhesive composition displaying an improved viscosity-temperatureprofile in comparison with the prior art. Another object of theinvention is an ionomer composition exhibiting greater viscositysensitivity to temperature change useful as a coating or sealant. Yetanother object of this invention is an acrylic hot melt pressuresensitive ionomeric adhesive exhibiting improved room temperature shearresistance. Another object of this invention is an acrylic hot meltpressure sensitive ionomeric adhesive composition exhibiting high roomtemperature shear resistance yet also exhibiting low viscosity atelevated application temperatures. Still another object of thisinvention is a hot melt pressure sensitive ionomeric adhesivecomposition exhibiting superior viscosity-temperature behavior incomparison with prior art compounds, while simultaneously exhibitingsuperior shear resistance as well as a good balance and other importantadhesive properties. Another object of this invention is to provide animproved tackifying resin composition for styrene-butadiene andstyrene-isoprene block copolymer adhesive compositions. These objectsand other objects which will become apparent below are met by thisinvention which comprises a polymer containing a monomer or monomerscontaining carboxylic acid residues, a metal salt capable increasingpolymer viscosity through the carboxylic acid residues located on thepolymer chains, and an o-methoxy aryl acid. In addition to use aspressure sensitive adhesives these compositions may be employed in manyapplications where it is desirable that the composition viscosity dependstrongly on temperature. For example, these compostions can be used astemperature dependent transmission fluids, encapsulating and pottingcompositions for electrical and electronic components and devices,caulking and sealant compositions, laminating adhesives, and coatingsfor wood, paper, metal, plastics, glass and other materials. Thelow-high temperature viscosity of the invention facilitates coating,application or fabrication at elevated temperatures, while the elevatedviscosity at low temperature is reflected in other improved physicalproperties.

DETAILED DESCRIPTION OF THE INVENTION

The compositions of this invention are comprised of at least 50% bytotal weight of the composition of a copolymer containing residues withpendant carboxylic acid functionality, a metal salt capable ofincreasing polymer viscosity through the carboxylic acid residues of thepolymer, and an o-methoxy-aryl acid. Many different organic polymers maybe used in preparing the compositions of this invention: acrylic,styrene-butadiene, butyl, ethylene-acrylic, ethylene-vinyl acetate andpropylene-higher olefin polymers may be used, as well as polyester,butene, isobutylene, isoprene and propylene polymers. Random copolymers,block copolymers, graft copolymers, interpentrating polymer networks,polymer solutions and physical polymer mixtures may be used. These maybe prepared from ethylenically unsaturated monomers such as ethylene,propylene, vinyl chloride, vinyl fluoride, vinylidene chloride,1,4-hexadiene, isobutylene, isoprene, chloroprene, styrene, vinylacetate, acrylonitrile, vinyl alcohol, butyl acrylate, butylmethacrylate, butadiene, and 2-ethylhexyl acrylate by free-radicalpolymerization. It is well known in the art that polyolefin componentsof hot melt adhesive compositions may be partially grafted with acidmonomers such as acrylic acids to increase the adhesive bonding of thehot melt compositions to nonporous metallic surfaces. See, e.g., U.S.Pat. Nos. 3,987,122, granted Oct. 19, 1976 and 3,868,433 granted Feb.25, 1975 to Bartz et al. Acid-grafted polyolefins may also be employedin the compositions of this invention. Condensation polymers such aspolyesters may also be used.

The copolymers of the instant invention are preferably prepared by thebulk or solution polymerization of acrylic or methacrylic acid estershaving up to 18 carbon atoms although minor amounts of otherethylenically unsaturated monomers may also be included. The preferredalkyl methacrylates and acrylates have an average of from one to about18 carbon atoms in the alkyl groups, and include methyl methacrylate,ethyl acrylate, butyl acrylate, butyl methacrylate, n-hexyl acrylate,heptyl acrylate, octyl methacrylate, nonyl acrylate, decyl acrylate, andthe various isomers of these acrylates and methacrylates such asiso-octylacrylate. One specific preferred alkyl acrylate for use in thisinvention is 2-ethylhexyl acrylate. Higher alkyl acrylates andmethacrylates, such as dicyclopentyloxyalkyl acrylates andmethacrylates, can in be used, particularly in combination with loweracrylates and methacrylates. Each of the polymer molecules of theinvention, whatever the exact nature of its ionomeric composition, mustcontain on the average at least one carboxylic acid bearing residue.However, 0.5-4% by weight of acidic residue is preferred. For example,at least one residue of acrylic, methacrylic, or acryloxypropionic acidmay be included. Non-acid bearing polymers may, however, also beincluded in the composition, as, for example, tackifying agents. Iftackifying polymers are not used, the monomer composition must beselected so that the polymer is tacky at the temperature at which thecomposition is to be used.

As is known in the art, the glass transition temperature (T_(g)) of thepolymer used to prepare a pressure sensitive hot melt adhesive must bebelow 0° C. in order for the composition to exhibit tack at roomtemperature. The glass transition temperature is a conventionalcriterion of polymer hardness and is described by Flory, Principles ofPolymer Chemistry, (Cornell University Press, 1953) at 56-57. The T_(g)of a copolymer of any specific composition can be approximatelycalculated from the T_(g) s of the corresponding homopolymer. Fox, Bull.Am. Physics Soc., 1,3, at 123 (1956). Consequently, the composition ofthe copolymer must be selected to give a T_(g) below 0° C. in order forthe composition to be useful as a pressure sensitive adhesive if notackifying polymer is included in the composition. The preferredmonomers can be blended to give the desired T_(g) of the copolymer. Forexample, a larger proportion (e.g., 58% by weight) of methylmethacrylate (T_(g) =105° C.) with a smaller proportion (e.g., 42%) ofN-octyl acrylate (T_(g) =-80° C.) provides a copolymer having thedesired T_(g). Most of the esters of acrylic acid and methacrylate acidhaving a low T_(g) are well known in the pressure sensitive adhesive artas monomers which confer tack on the corresponding polymer.

Other ethylenically unsaturated copolymerizable monomers having T_(g) ofabove 0° C. are a useful combination with the abovementioned tackifyingmonomers, provided they do not adversely affect the desired propertiesof the adhesive (e.g., unduly raise the overall T_(g)) and do notseriously interfere with the viscosity change effected by the metalsalt. These include vinyl acetate, styrene, vinyl toluene,methacrylamide, and N-methylolacrylacetamide. The proportions of themonomers fall within the following ranges:

    ______________________________________                                                     Approximate                                                                   Parts by Weight                                                                 Useful   Preferred                                                                              Most Preferred                               Monomer        Range    Range    Range                                        ______________________________________                                        Tackifying monomer                                                                           10-99.95 50-997   70-99.5                                      Unsaturated carboxylic                                                        acid monomer   0.05-20  0.3-10   0.5-6.0                                      Other monomers 0-89.95  0-49.7   0-29.5                                       ______________________________________                                    

Total of the monomers is 100 parts. These ranges, however, should not beconstrued as the only useful specification because the most importantcriteria are the glass transition temperature of the polymer and theproportion of carboxylic acid containing residues in the polymer.

If the composition is to be used for a laminating adhesive, compositionneed not exhibit tack at room temperature and the T_(g) of the polymermay be accordingly adjusted upward by an appropriate choice of themonomer composition. For example, a polymer having approximately thesame T_(g) as a homopolymer of butyl methacrylate (-50° C.) is useful ina laminating adhesive composition. Similarly, in other applications,such as electronic materials encapsulation and potting media, thepolymer must have a relatively high T_(g) (e.g., ˜100°-200° C.) and themonomer composition must be adjusted accordingly.

As is well known in the art, the preparation of the abovedescribedpolymers can be carried out using free radical-initiated polymerizationprocedures. These random polymers may be produced by solution or bulkpolymerization procedures. If the polymerization is carried out in thepresence of the solvent, the solvent can be stripped from the systembefore using as an adhesive. These polymers are preferably prepared bysolution polymerization. Before the solvent is stripped however, therelatively low viscosity of the solution is taken advantage of to addthe metal salt and o-methoxy-aryl acid component of the adhesivecomposition to the copolymer in order to effect a rapid and facilesolution of these materials in the polymer solution. Although noadditives are generally required, the following may be employed in thecomposition of this invention: Organic solvents such as toluene, xylene,acetone, methylethyl ketone, methylisobutyl ketone, halogenatedhydrocarbons such as chloroform, dichloroethane and the like; tackifyingagents, such as phenol resins, natural resins, coumarone-indene resins,resin ester and hydrated resin derivatives may be incorporated; fillersand pigments may be added to obtain needed properties. Typical fillersinclude: powdered quartz, barium sulfate, gypsum, calcium carbonate, andthe like. Antioxidants, ultraviolet inhibitors, plasticizers andpigments may also be employed.

A metal salt, as used throughout the specification and claims, isdefined to be a metal compound miscible with the polymer, irrespectiveof the extent of ionic character of the bonding between the metal atomand the remainder of the compound, and may be either a simple ioniccompound or a metal complex or a metal chelate, which is at leastpartially ionizable or soluble in the system. A miscible component ofthe composition is defined to be one which may be added to thecomposition without causing an otherwise transparent thin film (˜1 mils)of the composition to appear translucent. The metals are selected fromgroups: I A, I B, II A, II B, III B, IV B, V B, VI B, VII B, VIII, IIIA, IV A, V A, and VI A of the periodic table. Preferably, the metalsinclude: sodium, potassium, lithium, copper, gallium, tin, cerium,titanium, vanadium, chromium, molybdenum, manganese, iron, cobalt,nickel, berillium, cadmium, calcium, magnesium, zinc, zircronium,barium, strontium, aluminum, bismuth, antimony, lead, cobalt or anyother such metal which can be added to the composition by means of anoxide, hydroxide, or basic, acidic, or neutral salt or other compound orcomplex which is miscible with the polymer. Zinc, cadmium and zirconiumcompounds are preferred. The selection of metal and the anion aregoverned by the miscibility of the resultant metal complex or compoundwith the polymer medium employed. Examples of the organic and inorganicmetal salts and compounds include: carboxylic acid salts and chelates,such as zinc acetate, manganese tartrate, manganese benzoate, magnesiumcitrate, ferrous acetate, iron lactate, nickel acetate, cobalt acetate,cobalt benzoate, cobalt propionate, chelates or complexes which involvecoordinate bonding and may be partially ionizable such as the zincchelate of alanine or glycine, calcium chloride, aluminum diacetate,magnesium acetate, calcium carbonate, zirconium acetate, calciumacetate, calcium hydroxide, barium acetate, magnesium chloride,magnesium sulfate, ammonium complexes such as zinc ammonium benzoate,zinc ammonium carbonate or zinc ammonium sulfate, and the like. Anysulfur chelate having both ionic and coordination bonding in which themetal is sufficiently available or dissociable to bind to the carboxylicacid groups of polymer is useful. Polyvalent metal complexes (salts) oforganic acids that are capable of miscibility with or in the medium mayalso be employed. Such anions as acetate, glutamate, formate, carbonate,silicate, glycoate, octoate, benzoate, glutonate, oxylate, and lactateare satisfactory. The metal compound must be such that the metal isavailable to serve its viscosity increasing function; that is, it isdissociable to some extent to form the metal containing ion, or isattracted to the carboxyl groups by an equivalent mechanism. It is notintended that the invention be limited by theories or hypothesesconcerning the mechanism. "Crosslinking" or "viscosity increase" canboth be used to describe any of the possible phenomena or mechanisms bywhich the metal modifies the viscosity of the invention. The mostpreferred metal salt compounds include zinc octoate and zirconiumoctoate.

The metal compound is employed in an amount so that the ratio of metalto the carboxyl groups of the polymer varies from about 0.01 to about2.0 and preferably from about 0.05 to about 1.5. This is expressed on anequivalency basis as the ratio of metal (such as Zn⁺⁺ to --COOH groups,a ratio of 0.5 being stoichiometric, for divalent metal ions) to polymeracid.

The o-methoxy-aryl acid is defined to be monomeric or polymeric organiccompound which contains at least one o-methoxy aryl acid functionalgroup, defined to be a methoxy group and a carboxylic acid group bondedto adjacent carbon atoms which form a portion of an aromatic ringsystem, such that a carbon atom adjacent to the methoxy substitutedcarbon of the o-methoxy aryl acid functional group does not form a partof more than one aromatic ring and such that a carbon atom adjacent toeither carbon atom of the o-methoxy aryl acid group is not substitutedwith an alkoxy group.

Examples of aromatic rings systems are benzene, toluene, xylene,biphenyl, biphenylene, naphthalene, azulene, anthracene, phenanthracene,pyridine, aniline, pyrrole, furan, thiophene, indole, benzofuran,benzothiophene, quinoline, isoquinoline, carbazole, imidazole, acridine,thiazole, pyrazine, pyrimidine, pteridine, oxxazole, isoxazole,pyridazine, azepine benzothiozole, difuropyrazine, benzoquinoline andcoumarin.

Preferably, the o-methoxy-aryl acid is ##STR1## where R¹, R², R³ and R⁴are independently hydrogen, halogen, nitro, cyano, amino, (C₁ -C₈)alkyl,(C₁ -C₈)alkoxy, (C₁ -C₈)alkenyl, (C₅ -C₈)cycloalkyl, (C₅-C₈)cycloalkenyl, (C₅ -C₈)cycloalkynyl, (C₁ -C₈)alkynyl, (C₁-C₄)alkyloxy, (C₁ -C₄)alkyl phenyl or phenyl-(C₁ -C₄)alkyl optionallysubstituted with up to three substituents on the phenyl ring selectedfrom the group consisting of (C₁ -C₄)alkyl, (C₂ -C₄)alkenyl, (C₁-C₄)alkynyl, (C₁ -C₄)alkoxy, hydrogen, halogen, nitro, or cyano, or (C₁-C₄)alkyloxy (C₁ -C₄)alkyl; provided that neither R¹ nor R⁴ is (C₁-C₈)alkoxy, provided further that R¹, and R⁴ may, taken together, form a(C₄ -C₈)alkyl, (C₅ -C₈)alkenyl, (C₂ -C₄)alkoxy(C₂ -C₄)alkyl, or (C₅-C₈)alkynyl chain.

More preferably, the o-methoxy-aryl acid is given by Formula I above,where R¹, R², R³ and R⁴ are independently hydrogen, (C₁ -C₄)alkyl, (C₂-C₄)alkenyl, (C₂ -C₄)alkynyl, (C₁ -C₄)alkoxy, halogen, or phenyl,benzyl, or phenethyl where the phenyl ring is substituted with up to twosubstituents selected from the group consisting of hydrogen, (C₁-C₃)alkyl, and halogen, provided that neither R¹ nor R⁴ is (C₁-C₄)alkoxy.

Still more preferably, the o-methoxy-aryl acid is given by Formula Iabove, where R¹, R², R³ and R⁴ are independently hydrogen, methoxy, orchlorine, provided that neither R¹ nor R⁴ is methoxy.

Most preferably, the o-methoxy-aryl acid is 2-methoxybenzoic acid,2,4-dimethoxybenzoic acid, 4-chloro-2-methoxybenzoic acid, or3-methoxy-2-naphthenoic acid.

The composition contains between 0.001 and 20%, by weight of thepolymer, of the o-methoxy aryl acid. More preferably, the compositioncontains between 0.05 and 10% by weight of the polymer of the o-methoxyaryl acid. Still more preferably, the composition contains between 0.5and 4% by weight of the polymer of the o-methoxy aryl acid.

The preparation of the acrylate and other polymers of this invention iswell known to the art of synthetic polymer synthesis. See, generally, W.R. Sorenson and T. W. Campbell, Preparative Methods of Polymer Chemistry(Interscience Publishers, Inc., N.Y. 1961), 149-234 (AdditionPolymerization from Unsaturated Monomers) and especially 179-180(Polymerization of Methyl Acrylate); C. E. Schildknecht, Vinyl andRelated Polymers (John Wiley & Sons, Inc., N.Y. 1952), 220-224 (solutionpolymerization of methyl methacrylate); Copolymerization (G. E. Ham,ed., Interscience Publishers, N.Y.), Ch. XII, "CopolymerizationsInvolving Acrylates and Methacrylates as Principle Components", 673-674.Polymerization of the monomers can be effected in solution or in bulk,using free radical, cationic or anionic initiation, as is well known inthe art.

EXAMPLE 1 Acrylic Polymer Preparation

A monomer solution was prepared from 1056 g of butyl acrylate, 238 g ofbutyl methacrylate, and 26.4 g of methacrylic acid. An initiatorsolution was prepared from 4.1 g of t-butyl peroctoate, 104 g of tolueneand 26 g of acetone. To a flask equipped with a thermometer, a condensersurmounted with a nitrogen inlet, stirrer, and additional funnel wascharged with 100 g of toluene, 92 g of monomer solution and 9 g ofinitiator solution. The flask contents was kept under a nitrogen blanketand refluxed (117° C.) for 15 minutes. The remainder of the monomer andinitiator solutions were combined and fed into the refluxing flaskcontents over a one hour period. At the end of this feed, a charge of2.5 g of t-butyl peroctoate and 35 g of toluene was made to decrease thelevel of unreacted monomers. The polymer solution was diluted to 50%solids with 1478 g of toluene and cooled. When concentrated to 100%solids, the polymer was found to have a viscosity of 8400 cps at 175° C.The product was denoted as polymer A.

In a similar manner the polymers of polymers B-J of Table I wereprepared.

                  TABLE I                                                         ______________________________________                                        Acrylic Solution Polymers                                                     Polymer Monomer Composition (wt. percent)                                     ______________________________________                                        A       0.80 butyl acrylate/0.18 butyl                                                methacrylate/0.02 methacrylic acid                                    B       0.80 butyl acrylate/0.183 butyl methacrylate/0.017                            acrylic acid                                                          C       0.80 butyl acrylate/0.166 butyl methacrylate/0.034                            acryloxypropanoic acid                                                D       0.99 butyl acrylate/0.01 methacrylic acid                             E       0.98 butyl acrylate/0.02 methacrylic acid                             F       0.97 butyl acrylate/0.03 methacrylate acid                            G       0.97 2-ethylhexyl acrylate/0.03 methacrylic acid                      H       0.98 isodecyl methacrylate/0.02 methacrylic acid                              methacrylic acid                                                      J       0.68 isodecyl methacrylate/0.30 2-ethylhexyl                                  methacrylate/0.02 methacrylate acid                                   ______________________________________                                    

EXAMPLE 2 Acrylic Ionomer Composition Preparation

To 750 g of the polymer solution prepared in Example 1 were added 130 gof ethanol, 9.94 g of o-methoxybenzoic acid, and 26.7 g of zinc octoatesolution containing 8% zinc by weight. The resulting ionomer solutionwas mixed and concentrated to 100% solids. The viscosity at 175° C. was36,000 cps.

EXAMPLE 3 Ethylene-Acrylic Ionomer Composition Preparation

500 g of VAMAC (trademark of Du Pont de Nemours) VMR 5245 ethyleneacrylic ionomer, an elastomer prepared from methyl methylacrylate,ethylene, and carboxylic acid bearing monomers as well as a metal ion"crosslinker", is dissolved in 500 g of xylene. 20 g of o-methoxybenzoicacid is added with agitation to the polymer solution and the solution isstripped of solvent under vacuum to 80% solids. The resulting adhesivedisplays significantly better room temperature shear resistance than acomparable adhesive without the added o-methoxybenzoic acid.

EXAMPLE 4 Viscosity-Temperature Characteristics of p-Methoxybenzoic AcidAdhesive Composition

The viscosity of polymer A above was found to be approximately 8,000 cpsat 350° F. One equivalent of zinc octoate increased the viscosity toapproximately 80,000 cps. When one equivalent of p-methoxybenzoic acidwas added to the polymer containing one equivalent of zinc ion, theviscosity was reduced to approximately 18,000 cps. As illustrated in theFIGURE in which log viscosity is plotted versus reciprocal temperature,this viscosity reduction occurs over the entire temperature range from200° to 350° F.

However, if instead of p-methoxybenzoic acid, one equivalent ofo-methoxybenzoic acid was added to the zinc containing polymer thetemperature dependence of the viscosity had an entirely differentcharacter.

EXAMPLE 5 Viscosity-Temperature Characteristics of o-Methoxybenzoic AcidAdhesive Composition

The temperature dependence of the viscosity of the composition ofExample 2 had an entirely different character than that observed for thecorresponding p-methoxybenzoic acid-containing composition of Example 4.As is illustrated in the FIGURE, a significant viscosity reduction,comparable to that obtained with the addition of the p-methoxybenzoicacid, was obtained at high temperature. On the other hand, whentemperature was reduced the viscosity increased at a significantlygreater rate than was expected on the basis of the behavior of thepolymer containing the zinc and the p-methoxybenzoic acid. In fact, theviscosity of the p-methoxybenzoic containing polymer matches and thenexceeds that of the control which does not contain either methoxybenzoicacid.

EXAMPLES 6 Adhesive Properties of Acrylic Ionomer Compositions

Table II details the results of testing the adhesive properties of thecompositions based on polymer A described above.

Peel adhesion was measured in accord with the Pressure Sensitive TapeCouncil (PSTC) standard for "Peel Adhesion for Single Coated Tape 180°Angle," PSTC-1, revised 11/75. Shear resistance was measured in accordwith PSTC-7, revised 11/75, "Shear Adhesion (holding power)." Testequipment used in these tests was in accord with PSTC Appendage B andthe standard test conditions are in accord with PSTC Appendage A.Viscosity was measured with a Brookfield viscometer using an appropriatespindle. Rolling ball tack is measured in accord with PSTC-6.

Qualitative tack was a finger touch comparison executed by three or moreindividuals skilled in this art. The rating scale, from best to worseis: E (excellent), VG (very good), G (good), F (fair), P (poor) and O(none). Test specimens to be evaluated were compared with a standardconsisting of 3M Scotch Magic Mending Tape which is assigned a rating ofexcellent.

Table II illustrates that although the peel strength of the additivefree polymer A is significant (37 oz/in), the polymer exhibits noresistance to shear whatsoever. The adhesive properties whichcharacterize the polymer change when one equivalent of zinc ion has beenadded. Although the peel strength has been decreased somewhat (to 15-18oz/in), the material now exhibits significant shear resistance (24hours). Adding an equivalent of p-methoxybenzoic acid to this system, inaddition to the viscosity reduction illustrated in the FIGURE, effects asignificant increase in peel strength (to 58 oz/in). However,accompanying the reduction in viscosity, the shear resistance of thep-methoxy-benzoic acid containing system is reduced almost back to thelevel of the completely unmodified polymer (0.2 hours). On the otherhand, although one effect of adding an equivalent of o-methoxybenzoicacid to the zinc-Polymer A system was a very significant reduction inthe high temperature viscosity of the material, comparable to thatobtained with the other methoxy aryl acid p-methoxybenzoic acid, theshear resistance of the o-methoxybenzoic acid containing system of showsa significant increase (greater than a 100 hours) in contrast to thealmost complete loss of shear resistance to the p-methoxybenzoic acidcontaining system over Polymer A alone.

                                      TABLE II                                    __________________________________________________________________________    Adhesive Properties of Ionomer Compositions                                          p-Methoxy                                                                            o-Methoxy                                                       Zinc Octoate                                                                         benzoic acid                                                                         benzoic acid Peel.sup.a                                         (equivalents)                                                                        (equivalents                                                                         (equivalents Strength/                                                                            Shear.sup.a                                                                         Tack                                  on polymer                                                                           on polymer                                                                           on polymer                                                                           Viscosity                                                                           Failure                                                                              Resistance                                                                          (qualita-                             acid)  acid)  acid)  at 350° F.                                                                   Mode   (hours)                                                                             tive)                                 __________________________________________________________________________    0      0      0      5,000-                                                                              37 oz/in                                                                             0     E.sup.+                                                    8,000 cps                                                                           cohesive     F-A                                   1      0      0      80,000-                                                                             15-18 oz/in/                                                                         24    E-G                                                        100,000 cps                                                                         adhesive                                           1      1      0      18,000 cps                                                                          58 oz/in/                                                                            0.2   E                                                                cohesive                                           1      0      1      18,000-                                                                             12-18 oz/in                                                                          100   F-G                                                        25,000 cps                                                                          adhesive                                           __________________________________________________________________________     .sup.a Room temperature, 50% relative humidity.                          

EXAMPLES 7 Effect of Polymer Composition, Zinc Level ando-Methoxybenzoic Acid Level on Adhesive Properties

Table III details the effects of changes in the nature of the acidicmonomer incorporated into the polymer, the level of zinc ion, and thelevel of o-methoxybenzoic acid on the adhesive properties of the system.The adhesive properties of three acrylic polymers (A-1, B-1 and C-1),each containing an equivalent molar amount of a different carboxylicacid-bearing monomer, were tested. A comparison indicates that theadhesive properties of these materials are essentially the same. Eachexhibits excellent qualitative tack and substantial adhesive strength.The mode of failure is cohesive. Shear resistance, however, isnon-existent.

Comparison of these data with those for adhesive compositions A-2, B-2,and C-2 illustrate the effect of adding a half equivalent of zinc ion tothe system. The addition of zinc reduces the qualitative and rollingball tack, but increases the 180° peel adhesion strength of each of thesystems. In addition, each of the zinc-modified systems now exhibitssome shear resistance.

In adhesive compositions A-3, B-3 and C-3, the level of added zinc isincreased to a full equivalent on polymer acid. Again, the character ofthe change in adhesive properties is independent of the nature of thepolymer acid employed. The qualitative and rolling ball tack bothdecrease and the shear resistance increases. Each of these changes arein qualitative accord with the differences in adhesive propertiesapparent after the initial addition of a half equivalent of zinc.However, the 180° peel adhesion strength has decreased and the characterof failure has changed from cohesive to adhesive.

When a half equivalent of o-methoxybenzoic acid is added to the systemcontaining one-half equivalent of zinc ion (Compositions A-2, B-2, andC-2) the resulting compositions, A-4, B-4 and C-4, show an increase inshear resistance while tack and peel adhesive strength properties arerelatively unchanged. The increase in shear resistance is particularlysignificant for the methacrylic acid-containing system.

When a full equivalent of o-methoxybenzoic acid is added to thosesystems containing and equivalent of zinc ion (Compositions A-5, B-5 andC-5), a similarly significant increase in shear resistance is achieved;however, tack and peel strength of the systems containing theo-methoxy-benzoic acid appear to be slightly improved over those othersystems which do not contain this additive.

Finally, Composition A-6 shows the effect of adding an equivalent ofo-methoxybenzoic acid to the polymer A in the absence of zinc ion. Nosignificant differences are observed.

                                      TABLE III                                   __________________________________________________________________________    Effects of Polymer Acid Type, Zn.sup.++ Level and o-                          Methoxybenzoic Acid Level on Adhesive Properties                              Adhesive Composition                                                                          Adhesive Properties                                           Zn.sup.++ Level o-Methoxybenzoic                                                                       180°                                                   (Equivalents                                                                         Acid Level                                                                             Peel  Shear Re-                                                                           Rolling                                       Identi-                                                                           on Polymer                                                                           (Equivalents on                                                                        Strength                                                                            sistance                                                                            Ball                                                                              Qualitative                          Polymer                                                                            fication                                                                          Acid)  Polymer Acid)                                                                          (oz/in)                                                                             (hours)                                                                             Tack                                                                              Tack                                 __________________________________________________________________________    A    A-1 0      0        37C   0     2.8 E.sup.+                                   A-2 0.5    0        57C   1.9   4.4 VG.sup.+                                  A-3 1.0    0        11A   24    >7  G                                         A-4 0.5    0.5      55A   47    3.1 E                                         A-5 1.0    1.0      18A   >100  6 G                                           A-6 0      1.0      38C   0     2.8 E.sup.+                              B    B-1 0      0        29C   0     2.0 E.sup.+                                   B-2 0.5    0        55C   0.7   3.1 VG-E                                      B-3 1.0    0        20A   23    >7  F-G                                       B-4 0.5    0.5      45A   42    1.7 E                                         B-5 1.0    1.0      18A   >100  6.0 G                                    C    C-1 0      0        26C   0     1.0 E.sup.+                                   C-2 0.5    0        52C   0.1   3.9 E                                         C-3 1.0    0        19A   0.9   5.6 G                                         C-4 0.5    0.5      53C   0.2   7   E                                         C-5 1.0    1.0      28A   1.8   2   G-VG                                 __________________________________________________________________________

EXAMPLE 8 Preparation of Ethylene-Based Ionomer Composition

To 250 g of a copolymer of composition 85 parts by weight of ethylene, 5parts by weight of acrylamide, 10 parts by weight of t-butyl acrylateand 5 parts by weight of methacrylic acid is added 6 g of zincnaphthenate and 10 g of 4-chloro-2-methoxybenzoic acid by coextrusion at230° C.

EXAMPLE 9 Preparation of Grafted Acid-Olefinic Polymer Based IonomerComposition

To 250 g of isotactic polypropylene grafted with 6% acrylic acid andhaving a melt flow rate of 50 at 203° C. as measured according to ASTMMethod D-123-57T is added 5 g of zinc octoate and 10 g ofo-methoxybenzoic acid. The resulting composition exhibits decreasedviscosity at elevated temperature (400° F.) while maintaining good peeladhesion at room temperature to aluminum foil in comparison with acontrol composition without the o-methoxybenzoic acid.

EXAMPLE 10 Hot Melt Laminating Adhesive

In a manner similar to the preparation of polymer A of Example 1 above,a polymer of weight percent composition 0.98 n-butyl methacrylate and0.02 methacrylic acid is prepared. The polymer is dissolved in tolueneto form a 50% solids solution. To 500 g of this solution is added 15 gof cadmium octoate and 24 g of 3-methoxy-2 naphthenoic acid and 60 g ofethanol. The resulting ionomer solution is mixed and concentrated to100% solids. The resulting composition is useful as a hot meltlaminating adhesive.

I claim:
 1. A composition comprising(a) an organic polymer containing atleast one carboxylic acid group per polymer molecule, (b) a misciblemetal salt in a ratio of at least 10⁻³ moles of metal salt to moles ofpolymer carboxylic acid, (c) 10⁻² to 20% by weight, based on organicpolymer, of an o-methoxy aryl acid.
 2. A composition according to claim1 containing(a) at least 60% by weight of an organic polymer containingon the average at least one carboxylic acid group per polymer molecule,(b) at least one miscible metal salt in a ratio of from 1:10² to 10:1total moles of metal salt to moles of polymer carboxylic acid, and (c)0.10% to 10% by weight of polymer of an o-methoxy aryl acid.
 3. Acomposition according to claim 2 containing(a) at least 80% by weight ofan organic polymer containing on the average at least one carboxylicacid group per polymer molecule, (b) at least one miscible metal salt ina ratio of from 1:5 to 5:1 total moles of metal salt to moles of polymercarboxylic acid, and (c) 0.5% to 5% by weight of polymer of an o-methoxyaryl acid.
 4. A composition according to claim 1 containing(a) at least60% by weight of an organic polymer comprising at least 60% by weight ofmonomer residues selected from the group consisting of (C₁ -C₁₈)alkylesters of acrylic and methacrylic acid, and containing 0.1 to 10% byweight of carboxylic acid (b) at least one miscible metal salt such thatthe metallic portion is selected from the group consisting of Groups IA, II A, I B, II B, III B, IV B, V B, VI B, and VIII of the periodictable in a ratio of from 1:10² to 10:1 total moles of metal salt tomoles of polymer carboxylic acid, and (c) 0.10% to 10% by weight ofpolymer of an o-methoxy aryl acid.
 5. A composition according to claim 4containing(a) at least 80% by weight of an organic polymer comprising atleast 80% by weight monomer residues selected from a class consisting ofthe (C₁ -C₁₈)alkyl esters of acrylic and methacrylic acid and containing0.1 to 10% by weight of carboxylic acid bearing monomer residues, (b) atleast one miscible metal salt such that the metallic portion is selectedfrom the group consisting of Groups I A, II A, II B, I B, IV B VI B, VIIB and VIII of the periodic table in a ratio of from 1:10 to 10:1 totalmoles of metal salt to moles of polymer carboxylic acid, and (c) 0.10%to 10% by weight of polymer of an o-methoxy aryl acid.
 6. A compositionaccording to claim 5 containing(a) at least 80% by weight of an organicpolymer comprising at least 80% by weight monomer residues selected froma class consisting of the (C₁ -C₁₈)alkyl esters of acrylic andmethacrylic acid and containing 0.5 to 5% by weight of carboxylic acidbearing monomer residues, (b) at least one miscible metal salt such thatthe metallic portion is selected from the group consisting of Groups IA, II A, I B, II B, IV B, VI B, VII B and VIII of the period table in aratio of from 1:5 to 5:1 total moles of metal salt to moles of polymercarboxylic acid and, (c) 0.10% by weight of polymer of an o-methoxy arylacid.
 7. A composition according to claim 1 containing(a) at least 50%by weight of an organic polymer comprising at least 80% by weightmonomer residues selected from a class consisting of the (C₁ -C₁₈)alkylesters of acrylic and methacrylic acid and containing 0.1 to 10% byweight of carboxylic acid bearing monomer residues such that the glasstransition temperature of the polymer is less than 5° C., (b) at leastone miscible metal salt such that the metallic portion is selected fromthe group consisting of groups I A, II A, I B, II B, IV B, VI B, VII Band VIII of the periodic table in a ratio of from 1:10 to 10:1 totalmoles of metal salt per mole of polymer carboxylic acid and, (c) 0.10%to 10%, by weight of polymer, of an o-methoxy aryl acid.
 8. Acomposition according to claim 1 containing(a) an organic polymercontaining at least 60% by weight of monomer residues from the (C₁-C₁₈)alkyl esters of acrylic and methacrylic acid and containing in thecoverage at least one carboxylic acid group per polymer molecule, (b) atleast one miscible metal salt such that the metallic portion is selectedfrom the group consisting of Groups I A, II A, I B, II B, IV B, VI B,VII B, VIII of the periodic table in a ratio of from 1:10 to 10:1 totalmoles of metal salt per mole of polymer carboxylic acid, and (c) 0.10%to 10%, by weight of polymer, of an o-methoxy aryl acid having theformula ##STR2## where R¹, R², R³, and R⁴ are independently hydrogen,halogen, nitro, cyano, amino, (C₁ -C₄) alkyl, (C₁ -C₄)alkoxy, (C₁-C₄)alkenyl, (C₅ -C₈)cycloalkyl, (C₅ -C₈)cycloalkenyl, (C₅-C₈)cycloalkynyl, phenyl or phenyl-(C₁ -C₄)alkyl, optionally substitutedwith up to three substituents in the phenyl ring selected from the groupconsisting of (C₁ -C₄)alkyl, (C₂ -C₄)alkenyl, (C₂ -C₄)alkynyl, (C₁-C₄)alkoxy, hydrogen, halogen, nitro, or (C₁ -C₄)alkyloxy(C₁ -C₄)alkyl;provided that neither R¹ nor R⁴ is (C₁ -C₈)alkoxy; provided further thatR¹ and R⁴ may, taken together, form a (C₄ -C₈)alkyl, (C₅ -C₈)alkynyl, or(C₂ -C₄)alkoxy(C₂ -C₄)alkyl chain.
 9. A composition according to claim 8such that the substituents, R¹, R², R³, and R⁴ of the o-methoxy arylacid are independently hydrogen, (C₁ -C₄)alkyl, (C₂ -C₄)alkenyl, (C₂-C₄)alkynyl, (C₁ -C₄)alkoxy, halogen, phenyl, benzyl or phenethyl, wherethe phenyl ring is substituted with up to two substituents selected fromthe group consisting of hydrogen, (C₁ -C₃)alkyl, and halogen; providedthat neither R¹ nor R⁴ is (C₁ -C₄)alkoxy.
 10. A composition according toclaim 9 such that the substituents R¹, R², R³, and R⁴ of the o-methoxyaryl acid are independently hydrogen, methoxy or chlorine, provided thatneither R¹ nor R⁴ is methoxy.
 11. A composition according to claim 10such that the o-methoxy aryl acid is 2-methoxybenzoic acid,2,4-dimethoxybenzoic acid, 4-chloro-2-methoxybenzoic acid, or3-methoxy-2-naphthenoic acid.
 12. A composition according to claim 1containing(a) at least 50% by weight of an organic polymer containing atleast 80% by weight of monomer residues from the (C₁ -C₁₈)alkyl estersof acrylic and methacrylic acid and containing on the average at leastone carboxylic acid group per polymer molecule, (b) at least onemiscible metal salt such that the metallic portion is selected from thegroup consisting of zinc, zirconium and cadmium, in a ratio of from 1:10to 10:1 total moles of metal salt per mole of polymer carboxylic acid,and (c) 0.10% to 10%, by weight of polymer, of an o-methoxy aryl acidgiven by the formula ##STR3## where R¹, R², R³, and R⁴ are independentlyhydrogen, halogen, nitro, cyano, amino, (C₁ -C₈)alkyl, (C₁ -C₈)alkoxy,(C₁ -C₈)alkenyl, (C₅ -C₈)cycloalkyl, (C₅ -C₈)cycloalkenyl, (C₅-C₈)cycloalkynyl, phenyl or phenyl-(C₁ -C₄)alkyl, optionally substitutedwith up to three substituents on the phenyl ring selected from the groupconsisting of (C₁ -C₄)alkyl, (C₂ -C₄)alkenyl, (C₁ -C₄)alkynyl, (C₁-C₄)alkoxy, hydrogen, halogen, nitro, or (C₁ -C₄)alkyloxy(C₁ -C₄)alkyl;provided that neither R¹ nor R⁴ is (C₁ -C₈)alkoxy; provided further thatR¹ and R⁴ may, taken together, form a (C₄ -C₈)alkyl, (C₅ -C₈)alkenyl,(C₅ -C₈)alkynyl, or (C₂ -C₄)alkoxy(C₂ -C₄)alkyl chain, (d) optionalfillers, extender pigments, tackifying agents, organnic solvents,antioxidants, ultraviolet inhibitors, and plasticizers.
 13. Acomposition according to claim 1 containing(a) at least 80% by weight ofan organic polymer containing at least 80% by weight of monomer residuesfrom the (C₁ -C₁₈)alkyl esters of acrylic and methacrylic acids suchthat the glass transition temperature of the polymer is 0° C. or lessand which contains on the average at least one carboxylic acid group perpolymer molecule, (b) at least one miscible metal salt such that themetallic portion is selected from the group consisting of zinc, cadmium,zirconium, copper, magnesium, calcium, sodium, potassium, manganese,nickel and cobalt in a ratio of from 1:5 to 5:1 total moles of metalsalt per mole of polymer carboxylic acid, (c) 0.10 to 10%, by weight ofpolymer, of an o-methoxy-aryl acid given by the formula ##STR4## whereR¹, R², R³, and R⁴ are independently hydrogen, (C₁ -C₄)alkyl, (C₂-C₄)alkenyl, (C₁ -C₄)alkoxy, halogen, or phenyl, benzyl or phenethylwhere the phenyl ring is substituted with up to two substituentsselected from the group consisting of hydrogen, halogen and (C₁-C₃)alkyl provided that neither R¹ nor R⁴ is (C₁ -C₄)alkoxy, and (d)optional fillers, extender pigments, tackifying agents, organicsolvents, antioxidants, ultraviolet inhibitors and plasticizers.
 14. Acomposition according to claim 13 containing(a) at least 90% by weightof an organic polymer containing monomer residues selected from thegroup consisting of butyl acrylate, butyl methacrylate,2-ethylhexylacrylate, isodenyl methacrylate, acrylic acid, methacrylicacid and acryloxypropanoic acid such that the polymer contains between0.5% and 4% by weight of carboxylic acid residue, (b) a miscible metalsalt selected from the group consisting of zinc octoate, zincnaphthenate, cadmium octoate, and zirconium octoate, such that the ratioof metal to polymer acid groups is between 0.05 and 1.5 and between 0.5and 4%, by weight of polymer, (c) of an o-methoxy aryl acid selectedfrom the group consisting of 2-methoxybenzoic acid, 2,4-dimethoxybenzoicacid, 4-chloro-2-methoxybenzoic acid and 3-methoxy-2-naphthenoic acid.